YOU DIDN'T SAY HOW OLD YOUR HOUSE AND HEATING EQUIPMENT IS BUT I SUSPECT THAT YOUR DEMAND FOR HOT WATER HAS OUTSTRIPPED THE CAPACITY OF THE SYSTEM. YOU MAY NEED TO CONSIDER A POINT-OF-USE ON-DEMAND TANKLESS WATER HEATER (EITHER ELECTRIC OR GAS OR L.P. GAS)TO AUGMENT. THEY WILL PRODUCE HOT WATER AS LONG AS IT IS DEMANDED AND NOT WASTE HEAT ENRGY IN A RESERVOIR TANK SYSTEM.